The most obvious. But, also, the most maligned. A lot of people have misconceptions about the library. In fact, the other day, I heard a friend remark, "They don't carry any new-release books." To which my Information Science-studying girlfriend was heard to remark, "How IGNORANT are you?!" In fact, libraries, in order to compete, often ONLY carry new-release books. They want to offer what people want, what will get them into the building, and what will get people to support government funding of the institution. So they appeal to the masses by having a wide range of the books people want.
Furthermore, the library has changed a lot since you were forced to visit it on your 3rd-grade field trip. Most branches now offer online reservation and extensions.
It's also the cheapest solution to your book problem. The only money you have to pay is in late fees that are a whopping ten cents. And, since your hard-earned tax dollars are keeping the system alive, you might as well recoup some of your investment.